Q&A: Black Holes

Q:
I found the information on the center of our galaxy most intriguing, however, none of it tells me what the "lifecycle" of this phenomenon at the center of our galaxy is, and how it affects the rest of the galaxy. Can you tell me more about that?

A:
Understanding the life cycle of the supermassive black holes that are thought to be at the center of most galaxies, including our own, is a high priority in current astrophysical research. Recent research, including results from Chandra (see 3C294, Perseus Cluster, NGC 4636, Centaurus A) suggests that the energetic activity associated with supermassive black holes is intermittent, and depends on how much material is around for the black hole to feed on. For example, a black hole may be dormant for hundreds of millions of years, and then a collision of the black hole's host galaxy may provide a fresh supply of gas and dust. A few percent of the mass-energy that falls into the black hole will be converted to radiation and beams of high-energy particles that will clear out the area, slowing down the accretion process or stopping it. In this way, the black hole may regulate its own growth. The effect on the galaxy can be dramatic to the point of changing the structure of the galaxy and the rate at which stars form, or it can be rather mild and affect only a few hundred light years around the black hole, as appears to be the case in our galaxy.

Related Question: http://chandra.harvard.edu/resources/faq/black_hole/bhole-23.html